Phase I The long-term objective of this project is to improve the consistency and standardization of clinical cancer diagnostic testing of tissue biopsies. There are increasing numbers of cancer therapeutics that are linked to immunohistochemical diagnostic tests. Patient therapy is directly affected by the quantitative results of such testing. The absence of quantitative controls and calibrators seriously hampers the ability of laboratories to achieve consistent and standardized test results. Laboratories currently use pathologic discard tissue biopsies as controls, an inherently unstandardized source. In order to address this need, we developed the Analyte Controls technology. It provides an inexpensive, reproducible, and quantitative test material for detecting errors in staining procedure. This program aims to validate the clinical utility of this technology. In addition, this Phase I/Il Fast Track program is expected to lead to an FDA submission. For Phase I, we will address three technical aspects of the technology before launching into clinical trials. The Specific Aims of the Phase I grant are: (1) to create Analyte Controls for three new ER & PR antibodies. With these three, our Analyte Controls Slide will test for all of the commonly used ER and PR antibody clones, which is important prior to initiating clinical trials. (2) Identify Analyte Control peptides for ER and PR testing that distinguish pre-analytic sources of error (i.e., antigen retrieval) from analytic types of error, and (3) to demonstrate feasibility of a clinical laboratory slide densitometer that laboratories can use to quantify optical density of Analyte Controls on microscope slides. A method for precise quantification is required for clinical trials. The Analyte Controls for ER & PR will be the first quantitative control and calibrator for quantitative immunohistochemical testing that can be manufactured in inexhaustible amounts, relatively inexpensively, and in a reproducible fashion.